Point to point based backend communication layer for storage processing

ABSTRACT

A storage system is provided. The storage system includes a plurality of storage nodes, each of the plurality of storage nodes having a plurality of storage units with storage memory. The system includes a first network coupling the plurality of storage nodes and a second network coupled to at least a subset of the plurality of storage units of each of the plurality of storage nodes such that one of the plurality of storage units of a first one of the plurality of storage nodes can initiate or relay a command to one of the plurality of storage units of a second one of the plurality of storage nodes via the second network without the command passing through the first network.

BACKGROUND

Solid-state memory, such as flash, is currently in use in solid-statedrives (SSD) to augment or replace conventional hard disk drives (HDD),writable CD (compact disk) or writable DVD (digital versatile disk)drives, collectively known as spinning media, and tape drives, forstorage of large amounts of data. Flash and other solid-state memorieshave characteristics that differ from spinning media. Yet, manysolid-state drives are designed to conform to hard disk drive standardsfor compatibility reasons, which makes it difficult to provide enhancedfeatures or take advantage of unique aspects of flash and othersolid-state memory. Conformity to hard disk drive standards may causecommunication bottlenecks in solid-state drives and in storage systemsusing solid-state drives.

It is within this context that the embodiments arise.

SUMMARY

In some embodiments, a storage system is provided. The storage systemincludes a plurality of storage nodes, each of the plurality of storagenodes having a plurality of storage units with storage memory. Thesystem includes a first network coupling the plurality of storage nodesand a second network coupled to at least a subset of the plurality ofstorage units of each of the plurality of storage nodes such that one ofthe plurality of storage units of a first one of the plurality ofstorage nodes can initiate or relay a command to one of the plurality ofstorage units of a second one of the plurality of storage nodes via thesecond network without the command passing through the first network.

In some embodiments, a method for communicating in a storage system isprovided. The method includes communicating a command from a processorof a storage node to a processor of a first storage unit of the storagenode, wherein the storage node is coupled to further storage nodes ofthe storage system by a first network. The method includes communicatingregarding the command from the processor of the first storage unit to aprocessor of a second storage unit of one of the further storage nodesvia a second network coupling the first storage unit and the secondstorage unit.

In some embodiments, a storage system is provided. The system includes aplurality of storage nodes, each of the plurality of storage nodescoupled to each other of the plurality of storage nodes by a firstnetwork. The system includes a plurality of storage drives, each havingstorage memory, wherein each of the plurality of storage nodes includesone or more of the plurality of storage drives. The system includes atleast a subset of the plurality of storage drives coupled by a secondnetwork such that one of the plurality of storage drives included in afirst one of the plurality of storage nodes can initiate or relay acommand via the second network to one of the plurality of storage drivesincluded in a second one of the plurality of storage nodes.

Other aspects and advantages of the embodiments will become apparentfrom the following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIG. 1 is a perspective view of a storage cluster with multiple storagenodes and internal storage coupled to each storage node to providenetwork attached storage, in accordance with some embodiments.

FIG. 2 is a block diagram showing an interconnect switch couplingmultiple storage nodes in accordance with some embodiments.

FIG. 3 is a multiple level block diagram, showing contents of a storagenode and contents of one of the non-volatile solid state storage unitsin accordance with some embodiments.

FIG. 4 is a block diagram of a storage cluster, with storage nodescoupled together by a first network, and storage units, with storagememory, coupled together by a second network.

FIG. 5 is a block diagram of a storage cluster, with storage nodescoupled together by a first network, and a subset of storage unitscoupled together by a second network.

FIG. 6 is a flow diagram of a method for communicating in a storagesystem, which can be practiced using embodiments of the storage clusteras shown in FIGS. 4 and 5.

FIG. 7 is an illustration showing an exemplary computing device whichmay implement the embodiments described herein.

DETAILED DESCRIPTION

A storage cluster with storage nodes and storage units that have storagememory is herein described. Various embodiments of the storage clusterhave a first network that couples storage nodes, and a second networkthat couples some or all of the storage units. Embodiments of the firstnetwork are shown in FIG. 1, where the first network is described as aswitch fabric, in FIG. 2, where the first network is described as acommunications interconnect, and in FIGS. 4 and 5, where the firstnetwork is described in further detail. Embodiments of the secondnetwork are shown in FIG. 4 and FIG. 5 and described in detail. In someversions, the first network and the second network, while distinct fromone another in terms of communications paths, are integrated into thecommunications interconnect in a chassis, as shown in FIG. 2.

The embodiments below describe a storage cluster that stores user data,such as user data originating from one or more user or client systems orother sources external to the storage cluster. The storage clusterdistributes user data across storage nodes housed within a chassis,using erasure coding and redundant copies of metadata. Erasure codingrefers to a method of data protection or reconstruction in which data isstored across a set of different locations, such as disks, storage nodesor geographic locations. Flash memory is one type of solid-state memorythat may be integrated with the embodiments, although the embodimentsmay be extended to other types of solid-state memory or other storagemedium, including non-solid state memory. Control of storage locationsand workloads are distributed across the storage locations in aclustered peer-to-peer system. Tasks such as mediating communicationsbetween the various storage nodes, detecting when a storage node hasbecome unavailable, and balancing I/Os (inputs and outputs) across thevarious storage nodes, are all handled on a distributed basis. Data islaid out or distributed across multiple storage nodes in data fragmentsor stripes that support data recovery in some embodiments. Ownership ofdata can be reassigned within a cluster, independent of input and outputpatterns. This architecture described in more detail below allows astorage node in the cluster to fail, with the system remainingoperational, since the data can be reconstructed from other storagenodes and thus remain available for input and output operations. Invarious embodiments, a storage node may be referred to as a clusternode, a blade, or a server.

The storage cluster is contained within a chassis, i.e., an enclosurehousing one or more storage nodes. A mechanism to provide power to eachstorage node, such as a power distribution bus, and a communicationmechanism, such as a communication bus that enables communicationbetween the storage nodes are included within the chassis. The storagecluster can run as an independent system in one location according tosome embodiments. In one embodiment, a chassis contains at least twoinstances of both the power distribution and the communication bus whichmay be enabled or disabled independently. The internal communication busmay be an Ethernet bus, however, other technologies such as PeripheralComponent Interconnect (PCI) Express, InfiniBand, and others, areequally suitable. The chassis provides a port for an externalcommunication bus for enabling communication between multiple chassis,directly or through a switch, and with client systems. The externalcommunication may use a technology such as Ethernet, InfiniBand, FibreChannel, etc. In some embodiments, the external communication bus usesdifferent communication bus technologies for inter-chassis and clientcommunication. If a switch is deployed within or between chassis, theswitch may act as a translation between multiple protocols ortechnologies. When multiple chassis are connected to define a storagecluster, the storage cluster may be accessed by a client using eitherproprietary interfaces or standard interfaces such as network filesystem (NFS), common internet file system (CIFS), small computer systeminterface (SCSI) or hypertext transfer protocol (HTTP). Translation fromthe client protocol may occur at the switch, chassis externalcommunication bus or within each storage node.

Each storage node may be one or more storage servers and each storageserver is connected to one or more non-volatile solid state memoryunits, which may be referred to as storage units. One embodimentincludes a single storage server in each storage node and between one toeight non-volatile solid state memory units, however this one example isnot meant to be limiting. The storage server may include a processor,dynamic random access memory (DRAM) and interfaces for the internalcommunication bus and power distribution for each of the power buses.Inside the storage node, the interfaces and storage unit share acommunication bus, e.g., PCI Express, in some embodiments. Thenon-volatile solid state memory units may directly access the internalcommunication bus interface through a storage node communication bus, orrequest the storage node to access the bus interface. The non-volatilesolid state memory unit contains an embedded central processing unit(CPU), solid state storage controller, and a quantity of solid statemass storage, e.g., between 2-32 terabytes (TB) in some embodiments. Anembedded volatile storage medium, such as DRAM, and an energy reserveapparatus are included in the non-volatile solid state memory unit. Insome embodiments, the energy reserve apparatus is a capacitor,super-capacitor, or battery that enables transferring a subset of DRAMcontents to a stable storage medium in the case of power loss. In someembodiments, the non-volatile solid state memory unit is constructedwith a storage class memory, such as phase change or magnetoresistiverandom access memory (MRAM) that substitutes for DRAM and enables areduced power hold-up apparatus.

One of many features of the storage nodes and non-volatile solid statestorage is the ability to proactively rebuild data in a storage cluster.The storage nodes and non-volatile solid state storage can determinewhen a storage node or non-volatile solid state storage in the storagecluster is unreachable, independent of whether there is an attempt toread data involving that storage node or non-volatile solid statestorage. The storage nodes and non-volatile solid state storage thencooperate to recover and rebuild the data in at least partially newlocations. This constitutes a proactive rebuild, in that the systemrebuilds data without waiting until the data is needed for a read accessinitiated from a client system employing the storage cluster. These andfurther details of the storage memory and operation thereof arediscussed below.

FIG. 1 is a perspective view of a storage cluster 160, with multiplestorage nodes 150 and internal solid-state memory coupled to eachstorage node to provide network attached storage or storage areanetwork, in accordance with some embodiments. A network attachedstorage, storage area network, or a storage cluster, or other storagememory, could include one or more storage clusters 160, each having oneor more storage nodes 150, in a flexible and reconfigurable arrangementof both the physical components and the amount of storage memoryprovided thereby. The storage cluster 160 is designed to fit in a rack,and one or more racks can be set up and populated as desired for thestorage memory. The storage cluster 160 has a chassis 138 havingmultiple slots 142. It should be appreciated that chassis 138 may bereferred to as a housing, enclosure, or rack unit. In one embodiment,the chassis 138 has fourteen slots 142, although other numbers of slotsare readily devised. For example, some embodiments have four slots,eight slots, sixteen slots, thirty-two slots, or other suitable numberof slots. Each slot 142 can accommodate one storage node 150 in someembodiments. Chassis 138 includes flaps 148 that can be utilized tomount the chassis 138 on a rack. Fans 144 provide air circulation forcooling of the storage nodes 150 and components thereof, although othercooling components could be used, or an embodiment could be devisedwithout cooling components. A switch fabric 146 couples storage nodes150 within chassis 138 together and to a network for communication tothe memory. In an embodiment depicted in FIG. 1, the slots 142 to theleft of the switch fabric 146 and fans 144 are shown occupied by storagenodes 150, while the slots 142 to the right of the switch fabric 146 andfans 144 are empty and available for insertion of storage node 150 forillustrative purposes. This configuration is one example, and one ormore storage nodes 150 could occupy the slots 142 in various furtherarrangements. The storage node arrangements need not be sequential oradjacent in some embodiments. Storage nodes 150 are hot pluggable,meaning that a storage node 150 can be inserted into a slot 142 in thechassis 138, or removed from a slot 142, without stopping or poweringdown the system. Upon insertion or removal of storage node 150 from slot142, the system automatically reconfigures in order to recognize andadapt to the change. Reconfiguration, in some embodiments, includesrestoring redundancy and/or rebalancing data or load.

Each storage node 150 can have multiple components. In the embodimentshown here, the storage node 150 includes a printed circuit board 158populated by a CPU 156, i.e., processor, a memory 154 coupled to the CPU156, and a non-volatile solid state storage 152 coupled to the CPU 156,although other mountings and/or components could be used in furtherembodiments. The memory 154 has instructions which are executed by theCPU 156 and/or data operated on by the CPU 156. As further explainedbelow, the non-volatile solid state storage 152 includes flash or, infurther embodiments, other types of solid-state memory.

Referring to FIG. 1, storage cluster 160 is scalable, meaning thatstorage capacity with non-uniform storage sizes is readily added, asdescribed above. One or more storage nodes 150 can be plugged into orremoved from each chassis and the storage cluster self-configures insome embodiments. Plug-in storage nodes 150, whether installed in achassis as delivered or later added, can have different sizes. Forexample, in one embodiment a storage node 150 can have any multiple of 4TB, e.g., 8 TB, 12 TB, 16 TB, 32 TB, etc. In further embodiments, astorage node 150 could have any multiple of other storage amounts orcapacities. Storage capacity of each storage node 150 is broadcast, andinfluences decisions of how to stripe the data. For maximum storageefficiency, an embodiment can self-configure as wide as possible in thestripe, subject to a predetermined requirement of continued operationwith loss of up to one, or up to two, non-volatile solid state storageunits 152 or storage nodes 150 within the chassis.

FIG. 2 is a block diagram showing a communications interconnect 170 andpower distribution bus 172 coupling multiple storage nodes 150.Referring back to FIG. 1, the communications interconnect 170 can beincluded in or implemented with the switch fabric 146 in someembodiments. Where multiple storage clusters 160 occupy a rack, thecommunications interconnect 170 can be included in or implemented with atop of rack switch, in some embodiments. As illustrated in FIG. 2,storage cluster 160 is enclosed within a single chassis 138. Externalport 176 is coupled to storage nodes 150 through communicationsinterconnect 170, while external port 174 is coupled directly to astorage node. External power port 178 is coupled to power distributionbus 172. Storage nodes 150 may include varying amounts and differingcapacities of non-volatile solid state storage 152 as described withreference to FIG. 1. In addition, one or more storage nodes 150 may be acompute only storage node as illustrated in FIG. 2. Authorities 168 areimplemented on the non-volatile solid state storages 152, for example aslists or other data structures stored in memory. In some embodiments theauthorities are stored within the non-volatile solid state storage 152and supported by software executing on a controller or other processorof the non-volatile solid state storage 152. In a further embodiment,authorities 168 are implemented on the storage nodes 150, for example aslists or other data structures stored in the memory 154 and supported bysoftware executing on the CPU 156 of the storage node 150. Authorities168 control how and where data is stored in the non-volatile solid statestorages 152 in some embodiments. This control assists in determiningwhich type of erasure coding scheme is applied to the data, and whichstorage nodes 150 have which portions of the data. Each authority 168may be assigned to a non-volatile solid state storage 152. Eachauthority may control a range of inode numbers, segment numbers, orother data identifiers which are assigned to data by a file system, bythe storage nodes 150, or by the non-volatile solid state storage 152,in various embodiments.

Every piece of data, and every piece of metadata, has redundancy in thesystem in some embodiments. In addition, every piece of data and everypiece of metadata has an owner, which may be referred to as anauthority. If that authority is unreachable, for example through failureof a storage node, there is a plan of succession for how to find thatdata or that metadata. In various embodiments, there are redundantcopies of authorities 168. Authorities 168 have a relationship tostorage nodes 150 and non-volatile solid state storage 152 in someembodiments. Each authority 168, covering a range of data segmentnumbers or other identifiers of the data, may be assigned to a specificnon-volatile solid state storage 152. In some embodiments theauthorities 168 for all of such ranges are distributed over thenon-volatile solid state storages 152 of a storage cluster. Each storagenode 150 has a network port that provides access to the non-volatilesolid state storage(s) 152 of that storage node 150. Data can be storedin a segment, which is associated with a segment number and that segmentnumber is an indirection for a configuration of a RAID (redundant arrayof independent disks) stripe in some embodiments. The assignment and useof the authorities 168 thus establishes an indirection to data.Indirection may be referred to as the ability to reference dataindirectly, in this case via an authority 168, in accordance with someembodiments. A segment identifies a set of non-volatile solid statestorage 152 and a local identifier into the set of non-volatile solidstate storage 152 that may contain data. In some embodiments, the localidentifier is an offset into the device and may be reused sequentiallyby multiple segments. In other embodiments the local identifier isunique for a specific segment and never reused. The offsets in thenon-volatile solid state storage 152 are applied to locating data forwriting to or reading from the non-volatile solid state storage 152 (inthe form of a RAID stripe). Data is striped across multiple units ofnon-volatile solid state storage 152, which may include or be differentfrom the non-volatile solid state storage 152 having the authority 168for a particular data segment.

If there is a change in where a particular segment of data is located,e.g., during a data move or a data reconstruction, the authority 168 forthat data segment should be consulted, at that non-volatile solid statestorage 152 or storage node 150 having that authority 168. In order tolocate a particular piece of data, embodiments calculate a hash valuefor a data segment or apply an inode number or a data segment number.The output of this operation points to a non-volatile solid statestorage 152 having the authority 168 for that particular piece of data.In some embodiments there are two stages to this operation. The firststage maps an entity identifier (ID), e.g., a segment number, inodenumber, or directory number to an authority identifier. This mapping mayinclude a calculation such as a hash or a bit mask. The second stage ismapping the authority identifier to a particular non-volatile solidstate storage 152, which may be done through an explicit mapping. Theoperation is repeatable, so that when the calculation is performed, theresult of the calculation repeatably and reliably points to a particularnon-volatile solid state storage 152 having that authority 168. Theoperation may include the set of reachable storage nodes as input. Ifthe set of reachable non-volatile solid state storage units changes theoptimal set changes. In some embodiments, the persisted value is thecurrent assignment (which is always true) and the calculated value isthe target assignment the cluster will attempt to reconfigure towards.This calculation may be used to determine the optimal non-volatile solidstate storage 152 for an authority in the presence of a set ofnon-volatile solid state storage 152 that are reachable and constitutethe same cluster. The calculation also determines an ordered set of peernon-volatile solid state storage 152 that will also record the authorityto non-volatile solid state storage mapping so that the authority may bedetermined even if the assigned non-volatile solid state storage isunreachable. A duplicate or substitute authority 168 may be consulted ifa specific authority 168 is unavailable in some embodiments.

FIG. 3 is a multiple level block diagram, showing contents of a storagenode 150 and contents of a non-volatile solid state storage 152 of thestorage node 150. Data is communicated to and from the storage node 150by a network interface controller (NIC) 202 in some embodiments. Eachstorage node 150 has a CPU 156, and one or more non-volatile solid statestorage 152, as discussed above. Moving down one level in FIG. 3, eachnon-volatile solid state storage 152 has a relatively fast non-volatilesolid state memory, such as nonvolatile random access memory (NVRAM)204, and flash memory 206. In some embodiments, NVRAM 204 may be acomponent that does not require program/erase cycles (DRAM, MRAM, PCM),and can be a memory that can support being written vastly more oftenthan the memory is read from. Moving down another level in FIG. 3, theNVRAM 204 is implemented in one embodiment as high speed volatilememory, such as dynamic random access memory (DRAM) 216, backed up byenergy reserve 218. Energy reserve 218 provides sufficient electricalpower to keep the DRAM 216 powered long enough for contents to betransferred to the flash memory 206 in the event of power failure. Insome embodiments, energy reserve 218 is a capacitor, super-capacitor,battery, or other device, that supplies a suitable supply of energysufficient to enable the transfer of the contents of DRAM 216 to astable storage medium in the case of power loss. The flash memory 206 isimplemented as multiple flash dies 222, which may be referred to aspackages of flash dies 222 or an array of flash dies 222. It should beappreciated that the flash dies 222 could be packaged in any number ofways, with a single die per package, multiple dies per package (i.e.multichip packages), in hybrid packages, as bare dies on a printedcircuit board or other substrate, as encapsulated dies, etc. In theembodiment shown, the non-volatile solid state storage 152 has acontroller 212 or other processor, and an input output (I/O) port 210coupled to the controller 212. I/O port 210 is coupled to the CPU 156and/or the network interface controller 202 of the flash storage node150. Flash input output (I/O) port 220 is coupled to the flash dies 222,and a direct memory access unit (DMA) 214 is coupled to the controller212, the DRAM 216 and the flash dies 222. In the embodiment shown, theI/O port 210, controller 212, DMA unit 214 and flash I/O port 220 areimplemented on a programmable logic device (PLD) 208, e.g., a fieldprogrammable gate array (FPGA). In this embodiment, each flash die 222has pages, organized as sixteen kB (kilobyte) pages 224, and a register226 through which data can be written to or read from the flash die 222.In further embodiments, other types of solid-state memory are used inplace of, or in addition to flash memory illustrated within flash die222.

Storage clusters 160, in various embodiments as disclosed herein, can becontrasted with storage arrays in general. The storage nodes 150 arepart of a collection that creates the storage cluster 160. Each storagenode 150 owns a slice of data and computing required to provide thedata. Multiple storage nodes 150 cooperate to store and retrieve thedata. Storage memory or storage devices, as used in storage arrays ingeneral, are less involved with processing and manipulating the data.Storage memory or storage devices in a storage array receive commands toread, write, or erase data. The storage memory or storage devices in astorage array are not aware of a larger system in which they areembedded, or what the data means. Storage memory or storage devices instorage arrays can include various types of storage memory, such as RAM,solid state drives, hard disk drives, etc. The storage units 152described herein have multiple interfaces active simultaneously andserving multiple purposes. In some embodiments, some of thefunctionality of a storage node 150 is shifted into a storage unit 152,transforming the storage unit 152 into a combination of storage unit 152and storage node 150. Placing computing (relative to storage data) intothe storage unit 152 places this computing closer to the data itself.The various system embodiments have a hierarchy of storage node layerswith different capabilities. By contrast, in a storage array, acontroller owns and knows everything about all of the data that thecontroller manages in a shelf or storage devices. In a storage cluster160, as described herein, multiple controllers in multiple storage units152 and/or storage nodes 150 cooperate in various ways (e.g., forerasure coding, data sharding, metadata communication and redundancy,storage capacity expansion or contraction, data recovery, and so on).

FIG. 4 is a block diagram of a storage cluster 160, with storage nodes150 coupled together by a first network 402, and storage units 152, withstorage memory 406, coupled together by a second network 404. Thestorage memory 406 can include flash memory or other solid-state memoryas discussed above with reference to FIGS. 1-3 in some embodiments. Infurther embodiments, the storage memory 406 could include spinning mediasuch as a disk. It should be appreciated that in some embodiments, thestorage unit 152 is or acts as a storage drive. As described above withreference to FIGS. 1 and 2, the first network 402 could be implementedwith a switch fabric, an Ethernet bus, PCI Express, InfiniBand or othersuitable network or bus technology. As shown in FIG. 4, the CPUs 156 ofthe storage nodes 150 communicate with each other via the first network402. Storage units 152 may communicate with each other via secondnetwork 404. The second network 404 could be implemented with apoint-to-point network, which could also be referred to as a full meshor full mesh network, or a point to point backend communication physicallayer. The point-to-point network for the second network 404 isnon-switched and provides a non-shared I/O path in some embodiments. Infurther embodiments, the second network 404 is implemented as a switchfabric, or various further networks or busses. Each storage unit 152 cancommunicate with each other storage unit 152 via the second network 404,in the embodiment shown in FIG. 4. Further, as shown in FIG. 4, thesecond network 404 is distinct from the first network 402. Communicationfrom one storage unit 152 to another storage unit 152, via the secondnetwork 404, does not pass through the first network 402. This appliesgenerally to components of the storage cluster 160, and specifically tocommunications from a processor of a storage unit 152 to a processor ofa further storage unit 152.

FIG. 5 is a block diagram of a storage cluster 160, with storage nodes150 coupled together by a first network 402, and a subset of storageunits 152 coupled together by a second network 404. Embodiments of thefirst and second networks 402, 404, can use the various technologies asdiscussed above. In this variation, the second network 404 couples toone or more of the storage units 152 of each of the storage nodes 150,but does not couple together all of the storage units 152. For example,the second network 404 could couple one storage unit 152 of each storagenode 150 to one storage unit 152 of each other storage node 150, asshown in FIG. 5. In order to compensate for the lack of coupling of allstorage units 152, there is a forwarding unit 502 in each storage node150. FIG. 5 depicts the forwarding unit 502 as included in the CPU 156,which is symbolic of the CPU 156 forwarding an I/O command 504, as isthe case when the forwarding unit 502 is implemented as softwareexecuting on the CPU 156. In further embodiments, the forwarding unit502 could be implemented in firmware, hardware, or software or variouscombinations thereof.

Multiple communication scenarios are depicted in FIG. 5, using doubleheaded arrows with dashed lines. For various reasons, storage units 152communicate I/O commands 504 to and from each other. For example, in onescenario, a storage unit 152 receives a command or request from a CPU156 of a storage node 150, for some data from the storage memory 406 ofthat storage unit 152. The storage unit 152 experiences an error inreading a portion of error correcting code data (e.g., there are morebits in error in the data than can be corrected by the error correctingcode). The storage unit 152 requests other storage units 152 providedata, so that the storage unit 152 experiencing the error can regeneratethe data that the CPU 156 of the storage node 150 requested. In anotherscenario, a storage unit 152 completes an operation with the storagememory 406 of that storage unit 152, as a committed transactioninitiated by an authority 168 of a storage node 150. The storage unit152 sends information regarding the committed transaction to anotherstorage unit, via the second network 404. In yet another scenario, astorage unit 152 receives a command or request from a storage node 150,makes a decision regarding the command or the request, and communicateswith another storage unit 152 regarding the command or the request. Astorage unit 152 could relay a command or a request, received from astorage node 150, to another storage unit 152. Further scenariosinvolving a processor of a storage unit 152 communicating a command or arequest to a processor of another storage unit 152, based on receiving acommand or a request from a processor of a storage node 150, are readilydevised in keeping with the teachings herein.

In the above communication scenarios, a storage unit 152 could send anI/O command 504 via the second network 404 to another storage unit 152,if such a communication path is available via the second network 404. Astorage unit 152 could communicate with another storage unit 152 in thesame storage node 150, via the forwarding unit 502 in some embodiments.A storage unit 152 could communicate with another storage unit 152 viathe second network 404, through a storage unit 152, and finally to thedestination storage unit 152 via the forwarding unit 502 of a storagenode 150. Likewise, a storage unit 152 could communicate with anotherstorage unit 152 via the forwarding unit 502 of a storage node 150 andvia the second network 404. Further, a storage unit could communicatewith another storage unit 152 via a forwarding unit 502 of a storagenode 150, via the second network 404, and via the forwarding unit 502 ofanother storage node 150. Various further combinations of communicationusing the second network 404 and one or more of the forwarding units 502are readily devised in keeping with the teachings herein. It should beappreciated that each of these scenarios allows one storage unit 152 tocommunicate with another storage unit 152 without using the firstnetwork 402. In other words, the I/O command 504 (or othercommunication) from one storage unit 152 to another storage unit 152does not pass through the first network 402 in the various embodimentsdiscussed above.

FIG. 6 is a flow diagram of a method for communicating in a storagesystem, which can be practiced using embodiments of the storage clusteras shown in FIGS. 4 and 5. The method can be practiced by processors ina storage system, such as processors of storage nodes and processors ofstorage units. In an action 602, there is a communication from a firststorage node to a second storage node via a first network. For example,the communication could be regarding data or metadata in a storagecluster, and the first network could be implemented in various ways asdiscussed above. In an action 604, there is a communication from thefirst storage node to a first storage unit. For example, thecommunication could be regarding data or metadata in a storage cluster,and the communication could be over a bus or network coupling the firststorage node to the first storage unit. In an action 606, there is acommunication from the first storage unit to a second storage unit via asecond network. For example, the communication could be regarding orbased on the communication from the first storage node to the firststorage unit, and the second network could be implemented distinct fromthe first network and in various ways as discussed above. As noted abovethe second network may be implemented with a point-to-point network thatis non-switched and provides a non-shared I/O path in some embodiments.

It should be appreciated that the methods described herein may beperformed with a digital processing system, such as a conventional,general-purpose computer system. Special purpose computers, which aredesigned or programmed to perform only one function may be used in thealternative. FIG. 7 is an illustration showing an exemplary computingdevice which may implement the embodiments described herein. Thecomputing device of FIG. 7 may be used to perform embodiments of thefunctionality for a storage node or a non-volatile solid state storagein accordance with some embodiments. The computing device includes acentral processing unit (CPU) 701, which is coupled through a bus 705 toa memory 703, and mass storage device 707. Mass storage device 707represents a persistent data storage device such as a disc drive, whichmay be local or remote in some embodiments. The mass storage device 707could implement a backup storage, in some embodiments. Memory 703 mayinclude read only memory, random access memory, etc. Applicationsresident on the computing device may be stored on or accessed via acomputer readable medium such as memory 703 or mass storage device 707in some embodiments. Applications may also be in the form of modulatedelectronic signals modulated accessed via a network modem or othernetwork interface of the computing device. It should be appreciated thatCPU 701 may be embodied in a general-purpose processor, a specialpurpose processor, or a specially programmed logic device in someembodiments.

Display 711 is in communication with CPU 701, memory 703, and massstorage device 707, through bus 705. Display 711 is configured todisplay any visualization tools or reports associated with the systemdescribed herein. Input/output device 709 is coupled to bus 705 in orderto communicate information in command selections to CPU 701. It shouldbe appreciated that data to and from external devices may becommunicated through the input/output device 709. CPU 701 can be definedto execute the functionality described herein to enable thefunctionality described with reference to FIGS. 1-6. The code embodyingthis functionality may be stored within memory 703 or mass storagedevice 707 for execution by a processor such as CPU 701 in someembodiments. The operating system on the computing device may beMS-WINDOWS™ , UNIX™, LINUX™, iOS™, CentOS™, Android™, Redhat Linux™,z/OS™, or other known operating systems. It should be appreciated thatthe embodiments described herein may be integrated with virtualizedcomputing system also.

Detailed illustrative embodiments are disclosed herein. However,specific functional details disclosed herein are merely representativefor purposes of describing embodiments. Embodiments may, however, beembodied in many alternate forms and should not be construed as limitedto only the embodiments set forth herein. As noted above, the storageunits may be referred to as storage drives and the storage drives may beimplemented as solid state drives, e.g., flash arrays, or non-solidstate drives, e.g., hard disk drives.

It should be understood that although the terms first, second, etc. maybe used herein to describe various steps or calculations, these steps orcalculations should not be limited by these terms. These terms are onlyused to distinguish one step or calculation from another. For example, afirst calculation could be termed a second calculation, and, similarly,a second step could be termed a first step, without departing from thescope of this disclosure. As used herein, the term “and/or” and the “/”symbol includes any and all combinations of one or more of theassociated listed items.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “includes”, and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. Therefore, the terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

With the above embodiments in mind, it should be understood that theembodiments might employ various computer-implemented operationsinvolving data stored in computer systems. These operations are thoserequiring physical manipulation of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. Further, the manipulationsperformed are often referred to in terms, such as producing,identifying, determining, or comparing. Any of the operations describedherein that form part of the embodiments are useful machine operations.The embodiments also relate to a device or an apparatus for performingthese operations. The apparatus can be specially constructed for therequired purpose, or the apparatus can be a general-purpose computerselectively activated or configured by a computer program stored in thecomputer. In particular, various general-purpose machines can be usedwith computer programs written in accordance with the teachings herein,or it may be more convenient to construct a more specialized apparatusto perform the required operations.

A module, an application, a layer, an agent or other method-operableentity could be implemented as hardware, firmware, or a processorexecuting software, or combinations thereof. It should be appreciatedthat, where a software-based embodiment is disclosed herein, thesoftware can be embodied in a physical machine such as a controller. Forexample, a controller could include a first module and a second module.A controller could be configured to perform various actions, e.g., of amethod, an application, a layer or an agent.

The embodiments can also be embodied as computer readable code on anon-transitory computer readable medium. The computer readable medium isany data storage device that can store data, which can be thereafterread by a computer system. Examples of the computer readable mediuminclude hard drives, network attached storage (NAS), read-only memory,random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and otheroptical and non-optical data storage devices. The computer readablemedium can also be distributed over a network coupled computer system sothat the computer readable code is stored and executed in a distributedfashion. Embodiments described herein may be practiced with variouscomputer system configurations including hand-held devices, tablets,microprocessor systems, microprocessor-based or programmable consumerelectronics, minicomputers, mainframe computers and the like. Theembodiments can also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a wire-based or wireless network.

Although the method operations were described in a specific order, itshould be understood that other operations may be performed in betweendescribed operations, described operations may be adjusted so that theyoccur at slightly different times or the described operations may bedistributed in a system which allows the occurrence of the processingoperations at various intervals associated with the processing.

In various embodiments, one or more portions of the methods andmechanisms described herein may form part of a cloud-computingenvironment. In such embodiments, resources may be provided over theInternet as services according to one or more various models. Suchmodels may include Infrastructure as a Service (IaaS), Platform as aService (PaaS), and Software as a Service (SaaS). In IaaS, computerinfrastructure is delivered as a service. In such a case, the computingequipment is generally owned and operated by the service provider. Inthe PaaS model, software tools and underlying equipment used bydevelopers to develop software solutions may be provided as a serviceand hosted by the service provider. SaaS typically includes a serviceprovider licensing software as a service on demand. The service providermay host the software, or may deploy the software to a customer for agiven period of time. Numerous combinations of the above models arepossible and are contemplated.

Various units, circuits, or other components may be described or claimedas “configured to” perform a task or tasks. In such contexts, the phrase“configured to” is used to connote structure by indicating that theunits/circuits/components include structure (e.g., circuitry) thatperforms the task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. 112, sixth paragraph, for that unit/circuit/component.Additionally, “configured to” can include generic structure (e.g.,generic circuitry) that is manipulated by software and/or firmware(e.g., an FPGA or a general-purpose processor executing software) tooperate in manner that is capable of performing the task(s) at issue.“Configured to” may also include adapting a manufacturing process (e.g.,a semiconductor fabrication facility) to fabricate devices (e.g.,integrated circuits) that are adapted to implement or perform one ormore tasks.

The foregoing description, for the purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the embodiments and its practical applications, to therebyenable others skilled in the art to best utilize the embodiments andvarious modifications as may be suited to the particular usecontemplated. Accordingly, the present embodiments are to be consideredas illustrative and not restrictive, and the invention is not to belimited to the details given herein, but may be modified within thescope and equivalents of the appended claims.

What is claimed is:
 1. A storage system, comprising: a plurality ofstorage nodes, each of the plurality of storage nodes having storagememory; a first communication path coupling the plurality of storagenodes; and a second communication path coupled to the storage memory ofeach of the plurality of storage nodes such that the storage memory of afirst one of the plurality of storage nodes configured to initiate acommand to the storage memory of a second one of the plurality ofstorage nodes via the second communication path, wherein the firstcommunication path includes a switch fabric that couples the pluralityof storage nodes, the switch fabric distinct from the secondcommunication path.
 2. The storage system of claim 1, wherein thestorage memory comprises flash memory.
 3. The storage system of claim 1,wherein the second communication path comprises a non-switched,non-shared I/O path.
 4. The storage system of claim 1, wherein thesecond communication path is a mesh network.
 5. The storage system ofclaim 1, further comprising: each storage node having a processor,wherein processors of storage nodes are configured to communicate witheach other via a switch fabric of the first communication that isdistinct from the second communication path.
 6. The storage system ofclaim 1, further comprising: the storage memory of a storage nodecomprises a controller, wherein controllers of storage memory indiffering storage nodes are configured to communicate with each othervia the second communication path.
 7. The storage system of claim 1,wherein the storage memory within one of the plurality of storage nodescomprises a plurality of flash memory devices wherein at least two ofthe plurality of flash devices have differing storage capacities.
 8. Amethod for communicating in a storage system, comprising: communicatinga command from a processor of a storage node to a processor of a firststorage unit of the storage node, wherein the storage node is coupled tofurther storage nodes of the storage system by a first communicationpath, the first communication path comprising switch fabric that couplesstorage nodes of the storage system; and communicating regarding thecommand from the processor of the first storage unit to a processor of asecond storage unit of one of the further storage nodes via a secondcommunication path coupling the first storage unit and the secondstorage unit without the communicating regarding the command passingthrough the first communication path.
 9. The method of claim 8, whereinthe second communication path comprises a non-switched, non-shared I/Opath.
 10. The method of claim 8, wherein the communicating regarding thecommand from the processor of the first storage unit includescommunicating a request based on the command.
 11. The method of claim 8,wherein the second communication path is a point to point backendcommunication physical layer coupling each storage unit of each storagenode to each storage unit of each other storage node of the storagesystem.
 12. The method of claim 8, further comprising: completing anoperation with a first storage memory of the first storage unit as acommitted transaction.
 13. The method of claim 8, further comprising:sending information regarding the committed transaction from the firststorage unit to the second storage unit via the second communicationpath.
 14. A storage system, comprising: a plurality of storage nodes,each of the plurality of storage nodes coupled to each other of theplurality of storage nodes by a first communication path that includesswitch fabric; a plurality of storage drives, each having storagememory, wherein each of the plurality of storage nodes includes one ormore of the plurality of storage drives; and at least a subset of theplurality of storage drives coupled by a second communication pathwherein one of the plurality of storage drives included in a first oneof the plurality of storage nodes can initiate a command via the secondcommunication path to one of the plurality of storage drives included ina second one of the plurality of storage nodes, without the commandpassing through the first communication path.
 15. The storage system ofclaim 14, further comprising: one of the plurality of storage nodesconfigured to perform data striping across the plurality of storagenodes by transferring a portion of a data stripe to each other of theplurality of storage nodes via the second network.
 16. The storagesystem of claim 14, wherein the second communication path is a point topoint backend communication physical layer coupling each storage unit ofeach storage node to each storage unit of each other storage node of thestorage system.
 17. The storage system of claim 14, wherein the secondcommunication path includes a non-switched, non-shared I/O path couplingthe first one of the plurality of storage drives to the second one ofthe plurality of storage drives.
 18. The storage system of claim 14,wherein the first network includes a switch fabric that couples theplurality of storage nodes, the switch fabric distinct from the secondnetwork.
 19. The storage system of claim 14, wherein the secondcommunication path is a mesh network
 20. The storage system of claim 14,wherein each storage node has a processor, wherein processors of storagenodes are configured to communicate with each other via the switchfabric, wherein processors of storage units in differing storage nodesare configured to communicate with each other via the secondcommunication path.